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Mahogany Duns

Like most common names, "Mahogany Dun" can refer to more than one taxon. They're previewed below, along with 11 specimens. For more detail click through to the scientific names.

Mayfly Species Isonychia bicolor

These are pretty much always called Mahogany Duns.
This is by far the most important species of Isonychia. Many angling books once split its credit with the species Isonychia sadleri and Isonychia harperi, but entomologists have since discovered that those are just variations of this abundant species.

See the main Isonychia page for more about these intriguing mayflies.
Isonychia bicolor (Mahogany Dun) Mayfly NymphIsonychia bicolor (Mahogany Dun) Mayfly Nymph View 7 PicturesThis Isonychia bicolor nymph from the Catskills displays the prominent white stripe sometimes characteristic of its species. This is the first such specimen I've photographed, because members of the same species in the Upper Midwest have a more subdued stripe (and were once thought to be a different species, Isonychia sadleri). The striking coloration on this eastern nymph is more appealing.
Collected April 19, 2006 from in
Added to by on April 21, 2006
Female Isonychia bicolor (Mahogany Dun) Mayfly DunFemale Isonychia bicolor (Mahogany Dun) Mayfly Dun View 13 Pictures
Collected June 14, 2005 from in
Added to by on May 26, 2006
Male Isonychia bicolor (Mahogany Dun) Mayfly SpinnerMale Isonychia bicolor (Mahogany Dun) Mayfly Spinner View 15 PicturesI got several really nice pictures of this spinner. I also collected a female on the same trip.
Collected August 9, 2006 from in
Added to by on August 11, 2006

Mayfly Species Paraleptophlebia bicornuta

These are pretty much always called Mahogany Duns.
This important Western species is one of the few mayflies outside the Ephemeridae family to possess large tusks on the front of its head. It is also one of the largest species of Paraleptophlebia.

P. bicornuta is often reinforced by simultaneous hatches of the more common Paraleptophlebia debilis. The two duns appear virtually identical to the naked eye, though bicornuta usually has an edge in size.

Paraleptophlebia bicornuta is by far the widest distributed tusked species, though there are others. Telling the tusked species apart is very difficult and even entomological texts are largely ambiguous on the characters that differentiate them. Distribution records are probably the most reliable way for anglers to know with any probability what they are looking at. Check out the Paraleptophlebia packii and Paraleptophlebia helena hatch pages for more distribution information.
Paraleptophlebia bicornuta (Mahogany Dun) Mayfly NymphParaleptophlebia bicornuta (Mahogany Dun) Mayfly Nymph View 1 PicturesThis species is interesting because it is common in lakes as well as streams. It is one of the last species of the year to emerge in western Montana. Adults have been collected as late as October 15 weather permitting.
Collected July 31, 2007 from in
Added to by on June 26, 2011
Male Paraleptophlebia bicornuta (Mahogany Dun) Mayfly DunMale Paraleptophlebia bicornuta (Mahogany Dun) Mayfly Dun View 1 PicturesYou wonder sometimes how certain insects get their common names. This one is called the 'mahogany dun' for some unknown reason.
Collected October 5, 2011 from in
Added to by on October 6, 2011
Male Paraleptophlebia bicornuta (Mahogany Dun) Mayfly SpinnerMale Paraleptophlebia bicornuta (Mahogany Dun) Mayfly Spinner View 3 Pictures
Collected September 26, 2011 from in
Added to by on September 26, 2011

Mayfly Species Paraleptophlebia debilis

These are pretty much always called Mahogany Duns.
This widespread species can produce memorable hatches where it is locally abundant, especially in the West where it also tends to run larger in size. It loves the margins as is typical of most Leptophlebiidae species but has a greater tolerance for current. They are often found even in riffles. This is the most important species in the West.
Female Paraleptophlebia debilis (Mahogany Dun) Mayfly DunFemale Paraleptophlebia debilis (Mahogany Dun) Mayfly Dun View 3 PicturesSize: 9mm. These photos really highlight the brown pigmentation of the wing venation (Venation: The pattern in which the veins on the wings of an insect are arranged. It is usually one of the most useful identifying characteristics.), but in the hand the wings look to be a uniform smokey gray. - Entoman
Collected October 22, 2011 from in
Added to by on February 4, 2012

Mayfly Species Paraleptophlebia helena

These are pretty much always called Mahogany Duns.
This large species of Paraleptophlebia is one of the tusked group. Records indicate it is endemic (Endemic: where found; native to; belonging exclusively to or confined to a particular place) to California where it fills the niche taken by Paraleptophlebia bicornuta in neighboring states. It usually hatches with the more common and very similar looking duns of Paraleptophlebia debilis.

Mayfly Species Paraleptophlebia packii

These are pretty much always called Mahogany Duns.
This large western species is common in places. It is one of the few that has tusks and substitutes for the more common tusked Paraleptophlebia bicornuta in some locales, particularly the central Rockies in parts of Colorado, Utah, and Wyoming where they have been documented. Telling the tusked species apart is very difficult and even entomological texts are largely ambiguous on the characters that differentiate the nymphs. Angling texts relying on gill morphology (Morphology: The form and structure of an organism, or the study of the form and structure of organisms.), terga pattern, and tusk shape are dubious at best. For now, the angler's best bet is to rely somewhat on documented distribution.

Mayfly Species Paraleptophlebia praepedita

These are pretty much always called Mahogany Duns.
This species may reinforce hatches of Paraleptophlebia debilis.

Mayfly Genus Paraleptophlebia

These are often called Mahogany Duns.
There are many species in this genus of mayflies, and some of them produce excellent hatches. Commonly known as Blue Quills or Mahogany Duns, they include some of the first mayflies to hatch in the Spring and some of the last to finish in the Fall.

In the East and Midwest, their small size (16 to 20, but mostly 18's) makes them difficult to match with old techniques. In the 1950s Ernest Schwiebert wrote in Matching the Hatch:

"The Paraleptophlebia hatches are the seasonal Waterloo of most anglers, for without fine tippets and tiny flies an empty basket is assured."

Fortunately, modern anglers with experience fishing hatches of tiny Baetis and Tricorythodes mayflies are better prepared for the two region's Paraleptophlebia. It's hard to make sense of so many species, but only one is very important and others can be considered in groups because they often hatch together:
In the West, it is a different story. For starters the species run much larger and can be imitated with flies as large as size 12, often size 14, and rarely smaller than 16. Another difference is the West has species with tusks! Many anglers upon first seeing them think they are immature burrowing nymphs of the species Ephemera simulans aka Brown Drake. With their large tusks, feathery gills, and slender uniform build, it's an easy mistake to make. Using groups again:
Paraleptophlebia (Blue Quills and Mahogany Duns) Mayfly NymphParaleptophlebia (Blue Quills and Mahogany Duns) Mayfly Nymph View 6 Pictures
Collected February 7, 2004 from in
Added to by on January 25, 2006
Male Paraleptophlebia adoptiva (Blue Quill) Mayfly DunMale Paraleptophlebia adoptiva (Blue Quill) Mayfly Dun View 14 Pictures
Collected April 30, 2007 from in
Added to by on May 3, 2007
Male Paraleptophlebia adoptiva (Blue Quill) Mayfly SpinnerMale Paraleptophlebia adoptiva (Blue Quill) Mayfly Spinner View 7 PicturesBased on the pale longitudinal forewing veins (excepting the costals), dark middle terga (Tergum: the dorsal part of an abdominal segment or segments (terga). Also used to describe the entire abdominal dorsum or the thoracic dorsal segments of Odonata.), and genitalia (Burks '53), this specimen is P. adoptiva.
Collected May 9, 2007 from in
Added to by on May 18, 2007
Male Paraleptophlebia heteronea (Blue Quill) Mayfly AdultMale Paraleptophlebia heteronea (Blue Quill) Mayfly Adult View 1 Pictures
Collected May 16, 2012 from in
Added to by on May 18, 2012
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